EN
The paper discusses the biologically active compounds contained in onion (Allium cepa L.) such as thio− sulfinates and other organosulfur compounds, saponins and flavonoids as well as evaluates their biological role. Method for biofungicides preparation, whose essential element is an aqueous extract of onion, and the possibility of its application in forest nurseries are presented. Content of polyphenols (quercetin and its derivatives) in a biopreparation responsible for its biological activity is determined as well.